Local or global asymmetry in gait of people without impairments.

Using two consecutive gait cycles, simultaneous and bilateral kinetic gait data, the main objectives of this study were (a) to identify the main functional roles of ankle, knee and hip extensors/flexors, and (b) to determine whether the action taken by these muscle groups appears to be symmetric or not. Gait of our able-bodied subjects appears to be asymmetric with significant differences noted between each two corresponding peak muscle moment values. Using principal component analysis (PCA) as a curve structure detection method, task discrepancies were recognized when comparisons were made between each two corresponding representative moment curves at each joint (local asymmetry). Muscle moment behaved symmetrically when the right limb representative curve was compared to its corresponding principal component (PC) at the contralateral limb. Gait of able-bodied subjects appears to be symmetric, while control and propulsion were recognized as two major roles of the extensors and flexors (global gait asymmetry). Symmetrical behavior of the lower limbs should be considered a consequence of local asymmetry which indicates different levels of within and between muscle activities developed at each joint during gait cycles.